1. Field of the Invention
The present invention relates to an integrated circuit provided with a core unit and an input and output unit, and to an electronic appliance in which such a circuit is mounted.
2. Description of the Related Art
Recently, as the process becomes increasingly finer, the circuit scale tends to be larger. This has also caused an increase in leak current. In applications with serious demand for reduction in power consumption, as represented by battery-driven portable equipment such as a cell phone, power consumption occurring in a standby state of an IC is of a non-negligible magnitude. This is particularly true of a sound LSI, which is in a standby state much of the time.
Patent document No. 1 discloses a microcontroller integrated circuit that addresses the requirement for low power consumption by comprising a low-power standby function, while maintaining the integrity of input and output ports. The circuit includes a microcontroller core logic (hereinafter, simply referred to as a core logic), an input and output port logic adapted to store an output logic level, an interface logic connected between the core logic and the input and output port logic, and a power switch controlled by the input and output port logic.
[Patent document No. 1]
JP 2001-184330 A
In the circuit disclosed in patent document No. 1, the physical reliability at a node between the core logic and the input and output port logic may be impaired when power is turned off in the core logic. Further, there is a possibility that a leak current occurs.